A sewer backup in London Ontario can cause raw sewage and water to enter your basement or lowest drains, creating a health hazard and serious damage. Heavy rain, blockages, tree roots, or failing pipes can trigger a backup. Our 24/7 emergency plumbing dispatch connects you with plumbers who handle sewer backup cleanup, drain clearing, and repairs across London, St Thomas, Strathroy, Woodstock, Ingersoll, and Dorchester.
Signs of a Sewer Backup
- Multiple drains backing up at once (toilets, sinks, basement floor drain)
- Gurgling in toilets or drains when you run water elsewhere
- Unusual odours from drains or the basement
- Water or sewage coming up through the basement floor drain
- Slow drainage throughout the house after rain or heavy use
If you see or smell sewage, avoid contact and call for emergency service. For less severe clogged drain issues, see our drain cleaning London page. For water from a burst pipe instead of the sewer, see burst pipe repair London.
What To Do When You Have a Sewer Backup
- Avoid contact with sewage and standing water – Wear gloves and boots if you must be in the area; keep children and pets away.
- Stop using all drains and toilets – Don't flush toilets, run sinks, or use the washing machine until the backup is cleared.
- Turn off electricity in flooded areas – If water has reached outlets or the panel, shut off power to the affected area for safety.
- Call an emergency plumbing service – A plumber can clear the blockage, inspect the line, and advise on cleanup and prevention (e.g. backwater valve, sump pump).
Why Sewer Backups Happen in London Ontario
Older sewer lines in London and surrounding communities are often clay or cast iron. Over time they can crack, collapse, or be invaded by tree roots. Combined sewer systems can also overload during heavy rain, sending water and sewage back toward homes. Aging infrastructure, ground movement, and improper disposal of grease or wipes contribute to blockages and backups. Regular drain cleaning and camera inspections can help catch problems before they become emergencies.
If you also experience a toilet overflow or recurring clogs, our plumbers can diagnose whether the issue is local (one fixture) or in the main line.
Sewer Backup Repair and Prevention
After clearing a backup, a plumber may recommend hydro-jetting, root removal, or pipe repair. Installing a backwater valve can help prevent future backups from the municipal side. In flood-prone basements, a working sump pump is essential—see our sump pump repair London page for help with pump service and battery backups.
For any plumbing emergency—leaking pipes, water heater failure, or sewer backup—our emergency plumber London dispatch is available 24/7.
Get Help Now
Don't wait when you have a sewer backup or basement flooding. Call our 24/7 emergency plumbing dispatch for sewer backup service in London Ontario, or request help online. We connect you with licensed plumbers serving London, St Thomas, Strathroy, Woodstock, Ingersoll, and Dorchester.